Description of the Prior Art Systems
In order to more fully understand the invention hereinafter described it is necessary to understand the present methods of transferring brake torque (from brake to stationary structure) for different types of landing gear e.g., such as in single and twin axle gears for purposes of illustration.
Single and Twin Axle Gears
The simplest method of reacting brake torque from the brake to a stationary part of the gear, is by means of shear bolts in a flanged mounted construction. Typical configurations are shown in FIGS. 1 and 2 for single and twin axles respectively. FIG. 3 shows a typical arrangement of these shear bolts 10 relative to the brake hydraulic actuators, 11 and is common to both FIGS. 1 and 2. A hollow axle 12 is used for both types of gears, and is prevented from rotating relative to the gear inner cylinder 15 by a lock pin 13.
Application of the present invention for these types of gears is impractical as there is no relative rotation between the pressure plate assemblies 28 and the gear inner cylinder 15, during gear retraction, and consequently brake compensating links are not used. In addition, there is probably no requirement for main gear steering for these types of gears.
Gears with Two (or more) Axles
The most common of these gears is the four-wheeled truck type, but the more recent six wheeled truck arrangements (shown in FIGS. 4 and 5) are types of gears more likely to be utilized as aircraft get larger and heavier.
Landing gears with 4-wheel trucks cannot have rigid flange mounted brake connections, due to the rotation of the truck assembly 16 relative to the inner cylinder 15 during landing, taxiing, and during retraction. (Differences between FIGS. 4 and 6 illustrate this rotation.) This also applies to the fore and aft axles of 6-wheeled trucks. In these cases, the brake torque for each individual brake, is transmitted to the non rotating inner cylinder 15 by means of a pin jointed link, generally known as a brake compensating link 17 Fore and 17 Aft.
The brake compensating link pin joints are shown as 20, 21, and 22 in FIGS. 4 and 5, and are of course, left and right handed. In most brake designs the brake "Stator" assemblies 27 and 29 includes the brake pressure plates 28 which contains the brake hydraulic actuators, 11 and is held stationary against rotation (around the axle) by the Compensating Links 17 fore and 17 aft, during the braking operations. The pressure plate assembly, (although located on the axle, is allowed to revolve on that axle as the angle ".theta." varies during the gear retraction (see FIG. 6).
Problems with Prior Art Systems When Main Gear Steering is a Requirement
In order to meet the main gear steering requirements, brake compensating links 17 fore and aft, have to align with the steered wheels (see FIG. 8). Such a steering angle (20.degree. minimum) would be in excess of the angular movement of ball joints are used in brake compensating links, and which usually have operating limits of +/-15.degree. Max.
The presence of a conventionally installed brake compensating link 17 restricts the inboard excursion of the tire during main gear steering (see FIG. 8).
Full efficiency of brake compensation is not maintained when braking and steering occur simultaneously. Brake compensating links axle geometry deviates from a true parallelogram as the steering angle increases.